This article describes how to create an alias email address to mail merge on behalf of someone else such as your boss or someone else within your organization.
Open your Gmail account settings, and then follow these instructions to add a new Send mail as account or alias email address.
Click on one of the logos below to view Simple Mail Transfer Protocol (SMTP) settings for some popular services.
NOTE: If you are using another Gmail account as an alias email address, you need to enable Less Secure App Access.
Restart Mail Merge add-on, and then select your recently added alias email address:
In the Google Docs Mail Merge sidebar, click on Show Email Settings, and then select your alias email address from the From Email Account drop-down menu.
In the Google Sheets Mail Merge dialog box, select your alias email address from the From Email Account drop-down menu.
NOTE:
The From Email Account drop-down menu only appears in the Google Docs Mail Merge sidebar if you have already added an alias email address, as described in step 1 above.
The Send mail as feature does not allow you to send emails over SMTP using your own account or other accounts within your Google Workspace domain. Therefore, if you want to use a third-party email provider (such as SendGrid) to send emails over SMTP with your Gmail account, you need to set the provider's SMTP settings.